6‐Mercaptopurine‐Induced Fluorescence Quenching of Monolayer MoS2 Nanodots: Applications to Glutathione Sensing, Cellular Imaging, and Glutathione‐Stimulated Drug Delivery

Abstract Molybdenum disulfide (MoS 2 ) nanodots (NDs) with sulfur vacancies have been demonstrated to be suitable to conjugate thiolated molecules. However, thiol‐induced fluorescence quenching of MoS 2 NDs has been rarely explored. In this study, 6‐mercaptopurine (6‐MP) serves as an efficient quencher for the fluorescence of monolayer MoS 2 (M‐MoS 2 ) NDs. 6‐MP molecules are chemically adsorbed at the sulfur vacancy sites of the M‐MoS 2 NDs. The formed complexes trigger the efficient fluorescence quenching of the M‐MoS 2 NDs due to acceptor‐excited photoinduced electron transfer. The presence of glutathione (GSH) efficiently triggers the release of 6‐MP from the M‐MoS 2 NDs, thereby switching on the fluorescence of the M‐MoS 2 NDs. Thus, the 6‐MP‐M‐MoS 2 NDs are implemented as a platform for the sensitive and selective detection of GSH in erythrocytes and live cells. Additionally, thiolated doxorubicin (DOX‐SH)‐loaded M‐MoS 2 NDs (DOX‐SH/M‐MoS 2 NDs) serve as GSH‐responsive nanocarriers for DOX‐SH delivery. In vitro studies reveal that the DOX‐SH/M‐MoS 2 NDs exhibit efficient uptake by HeLa cells and greater cytotoxicity than free DOX‐SH and DOX. In vivo study shows that GSH is capable of triggering the release of DOX‐SH from M‐MoS 2 ND‐based nanomaterials in mice. It is revealed that the DOX‐SH/M‐MoS 2 NDs can be implemented for simultaneous drug delivery and fluorescence imaging.